On the GoPiGo web site showing the “complete” robot, (GoPiGo · GoPiGo.io), there is no way to order the GoPiGo-3 as a complete kit without the Raspberry Pi.
Note that the “core” does not include the extra goodies that the “complete” GoPiGo includes and there’s no way to order the “complete” kit w/o the Raspberry Pi.